1. Field of the Invention
The present invention relates to a computer-based simulation technique, and more particularly the present invention is related to a simulation technique adapted to a short-term prediction.
2. Description of the Related Art
In recent years, an intelligent transportation system as part of city planning has been actively studied particularly since the latter half of the '90s.
Recent particular needs include a real time road information processing technology, such as car flow adjustment, other road traffic control operation assistance, congestion prediction, and other information delivery to car navigation systems. Such road information processing is processed by, for example, a probe car data provided from a sensor attached to each operating car. Once probe car data becomes available, the next challenge is to use the probe car data to process traffic information in real time, such as the amount of traffic and the degree of road congestion.
Japanese Published Unexamined Patent Application No. 2000-163451 describes an environment prediction system including a computation apparatus that performs simulation calculation and an observation apparatus that collects observed data in predetermined positions within an area over which the simulation calculation is performed. In the system, the computation apparatus divides the simulation calculation area into a two-dimensional coordinate matrix, sets an initial value used in the simulation calculation at each coordinate, receives boundary conditions as input, and performs the simulation calculation based on the set initial values and the input boundary conditions to determine values of observation items at each coordinate after a predetermined period has elapsed. The observation apparatus collects observed data at predetermined coordinates after the predetermined period has elapsed, and the computation apparatus compares the values determined in the simulation calculation at the predetermined coordinates with the observed data provided from the observation apparatus. When the comparison shows any difference, the initial values and/or the boundary conditions are corrected, and the simulation calculation is performed again.
Japanese Published Unexamined Patent Application No. 2002-286860 describes a simulation apparatus that performs groundwater flow analysis in which groundwater flow is analyzed and substance movement analysis in which the movement of a substance in groundwater is analyzed by using a flow direction dispersion coefficient and a delay coefficient as substance transportation parameters along with a convection dispersion delay model under flow conditions obtained in the groundwater flow analysis. In the simulation apparatus, the flow direction dispersion coefficient aL represents dispersion of a target substance, which is an element in the convection dispersion delay model, in the groundwater with respect to the groundwater flow direction, and the delay coefficient Rd represents delay of the movement of the target substance in the groundwater with respect to the groundwater flow. The delay coefficient Rd is set to be a desired fixed value r0, and the flow direction dispersion coefficient aL is set to be a plurality of values. The simulation apparatus includes substance transportation analysis means and delay coefficient determination means. The substance transportation analysis means calculates a concentration distribution of the substance or the concentration of the substance at a specific point for each of the plurality of flow direction dispersion coefficients along an elapsed time axis. The delay coefficient determination means determines the flow direction dispersion coefficient by comparing the calculated results provided from the substance transportation analysis means with the substance concentration distribution measured at an analysis target location after an intended period m has elapsed as measured value information, selecting a calculation result most similar to the measured value information from the calculated results, and setting the flow direction dispersion coefficient used to acquire the selected calculation result as the flow direction dispersion coefficient. The delay coefficient determination means also determines the delay coefficient by using an elapsed period n corresponding to the selected calculation result and the elapsed period m in the measurement to calculate r0×m/n and setting it as the delay coefficient.
Japanese Published Unexamined Patent Application No. 9-128677 discloses a technology in which the timing at which a traffic signal is changed is optimized by detecting a traveling vehicle having a built-in traveling path measuring device, monitoring traffic based on traveling path data provided from the traveling path measuring device, using actual traffic signal timing data and a vehicle traveling model to change the traveling path in the model to be close to the measured traveling path, and using the model to perform a simulation.
Japanese Published Unexamined Patent Application No. 2004-118735 discloses an apparatus that precisely predicts traffic over a period from the present to a relatively far future. The apparatus includes a traffic calculator that performs a traffic flow simulation based on road network data, traffic signal data over the road network, and the amount of OD traffic to calculate the amount of traffic, a future prediction processor that predicts the amount of future traffic based on the amount of observed past traffic and the amount of current observed traffic, and an OD traffic estimator that corrects the amount of OD traffic used in the traffic calculator in such a way that the amount of calculated traffic coincides with the amounts of current observed and predicted traffic.
The conventional technologies, however, only disclose methods for performing a simulation while correcting a simulator based on a measured observation data, but the methods do not particularly suggest improvement in simulator accuracy.